564
FXUS66 KPQR 041748
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
948 AM PST Tue Nov 4 2025

Updated aviation discussion.

.SYNOPSIS...Trending drier on Tuesday before a warm front lifts
north across the area later Tuesday afternoon and evening. The
active weather pattern returns by Tuesday night as a strong low
pressure system develops offshore and sends a series of fronts
across the area. Expect widespread rain and gusty winds with
each frontal passage, though high winds not expected at this
time. There is around a 15-30% chance of thunderstorms on
Wednesday, highest at the coast. A few thunderstorms may be
marginally severe with the main threat being strong winds and
possibly weak waterspouts or tornados. In addition, minor tidal
overflow flooding is expected along portions of Highway 101 and
Fraser Road in Tillamook County around high tide on Wednesday
from 10 AM to 3 PM PST. Conditions likely trend drier late
Friday into Saturday.

&&

.SHORT TERM...Today through Wednesday night...A mostly dry period is
expected across the area into early Tuesday afternoon as a
transient upper level ridge moves overhead. This will be short
lived as the next system begins to enter the region late in the
afternoon in the form of a warm front lifting northward through
western Oregon. Light rain returns to the southern Willamette
Valley around 1 pm Tue and quickly spreads northward into the
Portland metro around 4 pm. a large trough setting up over the
northeast Pacific will support a deep surface low well offshore
west of British Columbia. The trough is expected to become
negatively tilted Tuesday night into Wednesday, turning the mid-
level flow more southwesterly. A cold front associated with the
aforementioned low will move through the region early Wednesday
morning. Snow level are only expected to fall to around
5500-6000 ft, so not anticipating any snow at pass levels.
However, a good bout of rain is expected with this system. IVT
values along the coast are expected to peak around 750 kg/m/s
and remain above 500 kg/m/s for close to 24 hours leading to a
moderate AR. IVT values inland around the foothills will be
lower, peaking short of 500 kg/m/s but staying above 250 kg/m/s
for 24-30 hours. Rainfall amounts from Tuesday evening through
Wednesday night will vary across the area due to terrain and
orographic enhancement. Coastal areas should expect 1.25-2.5
inches with locally higher amounts in the Coast Range, 0.75-1.0
inches in the interior lowlands and 1.0-2.0 inches in the
Cascades and Cascade Foothills with locally higher totals on the
highest peaks.

Gusty winds are also expected with this Wednesday system as
winds turn to the southwest from the south. There is a 10-25%
chance for wind gusts to reach 45 mph (Wind Advisory criteria)
from Salem southward in the Willamette Valley and a 10-20%
chance wind gusts along the coast reach 58 mph (High Wind
Warning criteria, no advisories for coastal areas). Most likely
will see wind gusts around 30-40 mph inland and 45-50 mph at the
coast, with gusts up to 55 mph along beaches and headlands.
This would be strong enough to result in some tree damage and
power outages, but would not be strong enough for widespread
downed trees and significant impacts.

With the cold front passing through the region Wednesday morning, an
unstable atmosphere will be in place come the afternoon and evening
hours leading to a 15-30% chance for thunderstorms. The environment
will be supportive of low-topped convection with the highest
probabilities along the coast through the threat extends areawide.
Guidance suggests "skinny" surface based CAPE peaking around 250-400
J/kg in the afternoon along with 0-3 km SRH between 150-250 m2/s2.
SPC has placed much of northwest Oregon, west of the Cascade crest
and part of southwest Washington in a marginal threat for severe
weather on Wednesday. Given the decent SRH, storms may rotate
and support weak waterspouts or tornados if they come onshore
with a 2- 4% probability mainly along the coast and extending
into the western Willamette Valley. The threat for wind is is
5-14% for areas west of the Cascade crest with a similar threat
for 1 inch or greater hail. /19

.LONG TERM...Thursday through Monday...The next system is
expected to move into the region on Thursday, bringing another
round of rain and gusty winds. Wind speeds with this front look
to be fairly similar to Wednesday, likely a smidge lower. This
frontal system is also on track to produce similar rainfall
amounts. WPC QPF amounts from 4am Thursday through 4am Friday
range between 0.75-1.0 inches for inland valleys, 1.0-2.0 inches
for the coast and Cascade foothills, and 2-3 inches for the
Coast Range and south WA/north OR Cascades. Given all the rain
that is forecast to fall prior to the system on Thursday, rising
river levels will be a concern. The main question that remains
is whether or not enough rain will fall for some rivers to reach
flood stage on Wednesday and/or Thursday. According to the
latest HEFS guidance, the probability for any given river to
reach minor flood stage is generally 10% or less, except a 15%
chance for the Wilson River near Tillamook. Another river of
concern would be the Grays River near Rosburg. Small creeks and
streams are more likely to see some minor flooding. Lastly,
minor urban flooding will also be possible, especially in low-
lying areas with poor drainage.

Rain chances remain in the forecast Friday, however ensemble
guidance suggests rain amounts will be lighter and less impactful.
WPC 500 mb cluster analysis shows good agreement for an upper level
ridge axis too be positioned along the west coast and into the PacNW
which would support dry conditions. Cluster analysis also shows
decent agreement in the ridge amplifying and the axis shifting
inland by late Sunday as a trough digs across the Pacific. An
increasing number of ensemble members do bring rain back into
the forecast on Sunday as deep troughing offshore pushes the
upper level ridge east toward the Rockies. However, agreement
among the clusters by Monday is quite low with nearly equal
chances for ridging, zonal flow and troughing over the PacNW.

&&

.AVIATION...Lingering stratus and fog will continue to dissipate
across the western Willamette Valley and terrain, becoming
widespread VFR by 18-20z Tue. Easterly winds mainly less than 10
kts, turning more toward the southeast this evening. One exception
is easterly winds through the western Columbia Gorge are causing
gusts up to 25-30 kts at KTTD through ~12z Wed. Gusts will increase
into the Portland area, including KPDX, by 21-23z Tue, and into SW
Washington after 00-03z Wed.

A strong low pressure system approaches this afternoon, with rain
progressing from south to north after 20z Tue, reaching the northern
valley and southwest Washington around 00z Wed. At this point,
guidance suggests CIGs will remain low- end VFR, though occasional
drops in vis to MVFR are possible in stronger showers.
Winds will increase with this weather system and shift southerly.
Along the coast, expect gusts up to 28-35 kts after 03-05z Wed.
For the Willamette Valley south of the Portland metro area, gusts up
to 20-25 kts are possible after 06z Wed.

KPDX AND APPROACHES...Predominately VFR cigs through the period.
Rain arrives after 22-23z Tue from the south, with low- end VFR
CIGs. Occasional drops in VIS to MVFR possible in heavier showers.
Easterly winds gradually increase throughout the day with gusts up
to 20-25 kt by 21z Tue as offshore pressure gradients tighten. Winds
remain elevated through the period. -03

&&

.MARINE...Southerly winds remain light this morning ahead of the
next system, around 10-15 kt with gusts up to 20 kt. By late
Tuesday morning, winds will shift more southeasterly as an
offshore pressure gradient sets up due to lower pressure over the
waters and higher pressure inland. This will counteract the
westerly swell, but breezier winds will increase wind waves.
Expect winds to turn more southerly Tuesday night as the low
pressure system approaches, 25-35 kt with gusts up to 45 kt across
all waters. Can`t rule out isolated storm force wind gusts up to
48 kt (10-15% chance), mainly over the outer waters beyond 10 NM.
Gale Warnings remain in effect from 1 PM Tue to 7 PM Wed for the
outer waters, and 7 PM Tue to 7 PM Wed for the inner waters. Seas
remain around 6-7 ft at 12 seconds on Tuesday, but rapidly build
to 15-18 ft at 13 seconds by early Wednesday morning as the
system moves in.

Winds ease Wednesday night following this first system, but still
remain breezy with gusts up to 25-30 kt. Though Gales are unlikely
Wednesday night into early Thursday morning (only 10% chance),
there is high confidence (>90% chance) that hazardous seas of 15
ft or greater will remain. Another system quickly enters the
waters Thursday, returning another round of Gale force wind gusts
up to 45 kt. There is still a 20-30% chance for isolated storm
force wind gusts up to 48 kt on Thursday, with the highest chances
across the inner waters out 10 NM due to the potential development
of a coastal jet. Guidance currently suggests a 15-25% chance for
seas of 20 feet or higher Wednesday-Thursday, with the highest
chances over the outer waters. Winds weaken and seas subside
toward the end of the week.      -10

&&

.BEACH HAZARDS...There is a Coastal Flood Advisory for minor
tidal overflow flooding during high tide from 10 AM to 3 PM
Wednesday for the Pacific County Coast, Clatsop County Coast, and
Tillamook County Coast. Minor flooding during high tide is
expected in the low lying areas near bays, sloughs, and the lower
reaches of the coastal rivers. This is due to total tide up to 12
feet at Toke point resulting in tide up to one foot above ground
level, total tide up to 11 feet at Tongue Point resulting in tide
up to one foot above ground level, and total tide up to 11 feet
at Garibaldi resulting in tide up to one foot above ground level.

Expect flooding along portions of Highway 101, including near
Raymond, Seaside, and Fraser Road in Tillamook County. Coastal
residents in the warned area should be alert for rising water and
take appropriate action to protect life and property. Remain out
of the water to avoid hazardous swimming conditions. Minor tidal
overflow is possible again on Thursday and Friday as active
weather coincides with the King Tides.      -10

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...Coastal Flood Advisory from 10 AM to 3 PM PST Wednesday for
     ORZ101-102.

WA...Coastal Flood Advisory from 10 AM to 3 PM PST Wednesday for
     WAZ201.

PZ...Small Craft Advisory from 1 PM this afternoon to 7 PM PST this
     evening for PZZ210-251>253.

     Gale Warning from 7 PM this evening to 7 PM PST Wednesday for
     PZZ210-251>253.

     Gale Warning from 1 PM this afternoon to 7 PM PST Wednesday for
     PZZ271>273.
&&


$$

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